1. Field of the Invention
The present invention relates to a method of making a magnetoresistive (MR) element utilizing a magnetoresistive multilayered film such as a tunnel-junction film, a spin valve film, or the like. In particular, the invention relates to a method of making a current-perpendicular-to-the-plane (CPP) structure magnetoresistive element in which a sensing electric current is allowed to penetrate through the magnetoresistive multilayered film in a perpendicular direction. The perpendicular direction is defined as a direction normal to the plane along which the magnetoresistive multilayered film extends.
2. Description of the Prior Art
In general, when a magnetoresistive element is to be made, a magnetoresistive (MR) multilayered film such as a so-called spin valve film, a tunnel-junction film, or the like is subjected to a dry etching process, for example. A resist film of a predetermined pattern is formed over the MR multilayered film in the dry etching process. When the dry etching process is effected, the MR multilayered film is removed over an area off the resist film. In this manner, the MR multilayered film is shaped into a predetermined contour.
The MR multilayered film is formed on the lower electrode in a so-called current-perpendicular-to-the-plane (CPP) structure magnetoresistive element. The upper electrode is formed on the MR multilayered film. When the upper electrode is to be formed, a so-called contact hole is formed in an insulation layer covering over the MR multilayered film. The upper electrode is allowed to contact the MR multilayered film through the contact hole.
A Au layer is formed to extend over the upper surface of the MR multilayered film in the CPP structure magnetoresistive element, for example. The Au layer exhibits a higher corrosion resistance to the etching gas during formation of the contact hole. The Au layer serves to protect the MR multilayered film from the etching gas during the etching process. The MR multilayered film can thus reliably be prevented from damages caused by the etching gas.
On the other hand, when the MR multilayered film is shaped into a predetermined shape as described above, the Au layer is subjected to a dry etching process. Scrapings or waste of the Au layer tends to adhere to the side surface of the MR multilayered film. The scrapings serve to establish an additional path for an electric current between the upper and lower electrodes. The sensing electric current may flow into the additional path around the MR multilayered film. A sufficient electric current cannot flow across the MR multilayered film, so that the magnetoresistive characteristic of the MR multilayered film gets deteriorated.